Conventional fire truck design locates the driver and occupant cab at the frame front region and the engine and transmission are located adjacent or within the cab. The engine transmission is usually connected by a drive shaft to the front of a fire pump gear box and the rear output of the pump gear box is connected to the differential driving the rear axle and wheels. The fire pump gear box functions as a split-shaft power takeoff and includes shifting means wherein the power from the engine is selectively used to drive the fire pump connected to the gear box or drive the vehicle rear wheels.
This type of conventional fire truck arrangement locates the engine in the cab area producing considerable noise and heat adjacent the occupied cab having a detrimental effect upon firemen riding in the vehicle and noise levels often exceed those considered to be safe.
To overcome these problems the assignee of the present invention has successfully lowered the cab noise and temperature levels by remotely locating the engine and transmission adjacent the vehicle rear wheels. The vehicle radiator, engine and transmission are located rearwardly of the rear wheels and reversed with respect to conventional installations wherein the output shaft of the transmission extends forwardly and is connected to a drive shaft driving the top part of a transfer case located intermediate the vehicle front and rear wheels. The drive shaft in the transfer case selectively connects to a drive shaft located in a fire pump gear box mounted upon the vehicle frame forwardly of the transfer case and rearwardly of the cab. The fire pump is close coupled to the gear box.
The transfer case includes a lower portion connected to the upper shaft by selectively operated gear means and the lower portion of the transfer case includes an output shaft which extends rearwardly and is connected to the vehicle rear wheels differential by a drive shaft system.
While this arrangement of the power train components locates the engine remotely from the cab and removes the noise and heat from the cab area, the use of the transfer case, and the need for three primary drive train shafts, substantially adds to the cost and weight of the fire truck power drive system, and also requires that the fire pump be mounted higher in relation to the vehicle frame rails than the standard pump mounting arrangement.
It is an object of the invention to provide a fire truck arrangement having a forward-located cab and a rear-mounted engine and transmission wherein the need for an intermediary transfer case for selectively driving the vehicle rear wheels or the fire pump is eliminated.
Another object of the invention is to provide a rear engine fire truck having a simplified drive train arrangement wherein the drive train includes a fire pump gear box located forwardly of the vehicle rear wheels and is directly connected to the engine transmission, the fire pump gear box further including an output shaft directly connected to the differential for the rear wheels.
Yet another object of the invention is to provide a fire truck arrangement having a rear-mounted engine and transmission wherein a fire pump gear box located intermediate the vehicle front and rear wheels is close coupled to a fire pump and includes an input shaft directly connected to the engine transmission and an output shaft directly connected to the vehicle rear wheels differential, the gear box including shifting structure whereby power from the engine may be selectively transferred to the fire pump or the vehicle rear wheels.
Yet another object of the invention is to provide a fire pump gear box for use with a rear-drive fire truck wherein a fire pump is close coupled and mounted upon the gear box and the gear box includes an input shaft directly connected to the engine transmission and an output shaft directly connected to the vehicle differential and drive wheels, and power train selecting means within the gear box selectively drives the fire pump or rear wheels.
In the practice of the invention a fire truck includes an elongated frame basically consisting of a pair of spaced parallel elements having a front region, a rear region and a central region therebetween. The vehicle front steerable wheels are mounted upon the frame front region while the drive wheels are located at the rear region and are mounted upon axles driven through a conventional differential. A cab is located upon the frame front region including the drivers' conventional apparatus such as steering wheel, gear shift, brake operator, clutch, instruments, and the like. The cab also includes seats and compartments wherein the firemen ride, and the cab may be mounted substantially over the steering wheels extending forwardly and rearwardly thereof.
The engine is mounted upon the rear portion of the frame behind the rear wheels, and the engine is closely connected to a conventional transmission having an output shaft which extends toward the frame front region. The engine and transmission are of conventional construction, but are mounted on the frame in a "backward" manner as compared to a conventional installation.
A fire pump gear box is mounted on the frame intermediate the front and rear regions and intermediate the front and rear wheels. The gear box includes an input shaft extending rearwardly toward the engine transmission and is connected to the transmission output shaft by an elongated drive shaft and universal joint assembly. The gear box also includes a rearwardly extending output shaft located below the gear box input shaft and the gear box output shaft extends rearwardly toward the differential for the rear wheels and is connected thereto by a second elongated drive shaft and universal joint assembly.
A water pump, herein referred to as the fire pump, is closely coupled to the fire pump gear box and the gear box includes a fire pump drive shaft located above the gear box input shaft constituting an extension of the pump impeller. Internally, the gear box input shaft is splined and a drive gear is keyed thereon for selective axial displacement by a fork shifter wherein the drive gear may be shifted between a gear box output shaft drive position and a fire pump drive shaft drive position. The gear box output shaft includes a gear keyed thereto which meshes with the gear box input shaft drive gear when it is desired to drive the vehicle rear wheels, and the fire pump shaft includes a gear which meshes with the gear box input shaft drive gear when pumping is required. The gear box output shaft gear and fire pump shaft gear are radially misaligned wherein only one or the other may be in a driven relationship to the input shaft drive gear.
An idler lubricating gear is rotatably mounted upon the gear box output shaft for meshing with the input shaft drive gear when the drive gear is meshed with the fire pump drive gear. Lubricating oil within the gear box is transferred by the idler gear to the input shaft and pump drive gears and the bearings for the fire pump shaft eliminating the necessity for expensive lubrication pump apparatus.
As the fire pump gear box is directly connected to the engine transmission, and is also directly connected to the vehicle rear wheels differential, the fire pump gear box eliminates the necessity for an expensive transfer case intermediate the engine and fire pump gear box for transmitting power to the differential and the invention substantially reduces the weight of the vehicle drive train and the noise level thereof.